The present invention relates generally to internal combustion engines and, more particularly, to an engine control unit enablement system that stores electrical energy upon engine shut-down such that at a subsequent engine start-up the engine control unit may be powered nearly instantaneously.
Rope-start, two-stroke engines are used in a variety of applications including outboard marine engines, snowmobiles, PWCs, ATVs, motorcycles, and lawn and garden equipment. These engines are started by manually actuating a starter mechanism that drives the engine to rotate. Engine rotation initiates a firing sequence by enabling the supply of electrical power to the engine's fuel injection and/or ignition systems that are dynamically controlled by an engine control unit. The most common manually actuated starter mechanism includes a rope that is wound around a spool coupled to the engine's flywheel either directly or via one or more gears. The rope unwinds from the spool when it is pulled by the operator, thereby driving the spool and the flywheel to rotate thereby initiating combustion.
Consumers demand that rope engines start with as little manual input as necessary. It is preferred that the engine start on the first pull. Accordingly, engine control units are used to control fuel injection and/or ignition systems to optimize engine start-up and engine running. Not only does the engine control unit improve engine start-up, the engine control unit manages engine operation so as to optimize engine operation. Accordingly, the engine control unit is programmed to assess engine operation from a myriad of sensors and, based on that feedback, control engine operation to satisfy stringent environmental concerns, fuel efficiency requirements, reduce noise emission, and meet the power loads placed on the engine.
In particular, some modern engines, such as the EVINRUDE® outboard motor, have fuel injectors that are designed to operate at rather high voltages that exceed that which can be provided by standard 12 volt systems. EVINRUDE is a registered trademark of the present assignee. These injectors operate extremely fast and responsive, and are not only state-of-the-art in terms of performance, they are so highly tuned that engines so equipped greatly exceed environmental emissions standards for years to come. However, to obtain such exacting performance, the injectors operate at a rather high voltage, preferably 55 volts.
To provide the requisite higher voltages to power these fuel injectors and other systems of the engine, alternators are commonly used to translate the engine's mechanical energy to electrical energy. The electrical energy, once properly conditioned, may then be used to drive the fuel injectors and/or other electronics of the engine or motor. Accordingly, these newer 55 volt systems require more robust alternators and electronics to control not only the high voltage components, but also any lower voltage components, such as 12 volt fuel and oil pumps. With a rope-start engine, it is difficult to apply a pulling force on the rope to induce generation of electrical energy sufficient to supply all these needs on just one pull. As such, the operator may be required to make several pulls.
Generally, when the engine is running, the alternator converts mechanical energy of a rotating engine to electrical energy. In this regard, the alternator provides an AC output that is input to a rectifier to convert the AC output of the alternator to DC. The DC output of the rectifier is then fed to a filter capacitor to remove transients in the DC output of the rectifier. The output of the filter capacitor is then used to form a DC rail voltage that is used to power the engine and motor electronics. In other words, during engine running, the filter capacitor is charged. However, when the engine stops running, the capacitor, which is constantly connected to the various engine electronics across the voltage rail, is drained of its stored energy. As such, after the engine stops running, the capacitor continues to provide a rail voltage for a brief period of time, usually milliseconds, until it is completely drained or depleted of its stored energy. Accordingly, in an engine restart, the filter capacitor must be recharged to provide the requisite rail voltage for engine component operation. For rope-start engines with high current demands and/or higher voltage requirements, this can be particularly difficult.
A number of techniques have been developed to improve and ease the starting of rope-start engines. One such technique is described in commonly assigned U.S. Ser. No. 09/579,973. Notwithstanding the advancements of these improved starting techniques, with the advent of higher voltage requirements and/or high current needs, there is room for improvement.
It would therefore be desirable to design a system to maintain electrical charge in an energy storage device to ease and improve starting of an engine.